Background
In 2019, the World Health Organization (WHO) identified vaccine hesitancy, defined as the “delay in acceptance or refusal of vaccination despite the availability of vaccine services” [Reference MacDonald, Eskola, Liang, Chaudhuri, Dube and Gellin1], as one of the 10 threats to global health [2]. Although there have always been people hesitant towards receiving vaccinations, this threat has only increased since the beginning of the COVID-19 pandemic [Reference MacDonald, Eskola, Liang, Chaudhuri, Dube and Gellin1, Reference Shapiro, Tatar, Dube, Amsel, Knauper and Naz3–Reference Santoli, Lindley, DeSilva, Kharbanda, Daley and Galloway6]. For example, a dramatic decrease in the administration of measles-containing vaccines, especially in children older than 24 months, was observed from March 16, 2020 to April 19, 2020 [Reference Santoli, Lindley, DeSilva, Kharbanda, Daley and Galloway6] The rapidity of the COVID-19 vaccine development and concerns regarding the vaccine’s safety certainly have contributed to the lack of vaccine confidence [Reference McCready, Nichol, Steen, Unsworth, Comparcini and Tomietto7, Reference Nehal, Steendam, Ponce, van der Hoeven and Smit8]
Several factors have been found to be associated with vaccine hesitancy towards the COVID-19 vaccine, such as sociodemographic (e.g., education), health-related (e.g., vaccination history/medical conditions), and vaccine-related (e.g., concerns about the safety or quality of the vaccine) factors [Reference Kafadar, Tekeli, Jones, Stephan and Dening9]. However, conspiracy theories (CTs) are another important factor associated with vaccine hesitancy. Moreover, CTs even have been identified as the strongest predictor of anti-vaccination attitudes [Reference Hornsey, Harris and Fielding10].
CTs can be defined as secret plans hatched by powerful groups (“elites”) with the intention to harm society or a specific group of people, often to the benefit of the powerful group [11–Reference Robertson, Pretus, Rathje, Harris and Van Bavel13]. While many CTs are unjustified or irrational beliefs, as they have little or no evidence [Reference Magarini, Pinelli, Sinisi, Ferrari, De Fazio and Galeazzi14], some CTs may become plausible for people with a deep-rooted mistrust of government, medicine, and/or science, caused by countless historical examples of abuse or historical marginalization, or for people within certain socio-economic or political situations, such as a lack of economic vitality and undemocratic regimes [Reference Hornsey, Harris and Fielding10].
Despite their scientific and medical training, healthcare workers (HCWs) and healthcare students have been identified as a sub-group displaying considerable hesitancy towards accepting a COVID-19 vaccine [Reference McCready, Nichol, Steen, Unsworth, Comparcini and Tomietto7, Reference Mustapha, Khubchandani and Biswas15, Reference Biswas, Mustapha, Khubchandani and Price16]. Although the prevalence of COVID-19 vaccination hesitancy in HCWs varied widely, a large-scale review published in 2021 found that among HCWs (n = 76,471) more than a fifth of HCWs worldwide reported COVID-19 vaccination hesitancy [Reference Biswas, Mustapha, Khubchandani and Price16]. The vaccine hesitancy rate among healthcare students is almost equal to the hesitancy rate in practicing HCWs [Reference Mustapha, Khubchandani and Biswas15]. Limited information, however, exists about the prevalence and determinants of COVID-19-related CTs in HCWs and healthcare students worldwide. The purpose of this study therefore was to conduct a scoping review to map out the evidence base pertaining to (1) the prevalence of COVID-19-related CTs among HCWs and healthcare students worldwide, and (2) the nature and determinants of conspiracy thinking among HCWs within the context of the COVID-19 pandemic. Getting insight into the factors contributing to these beliefs among this population is pivotal as HCWs COVID-19 vaccine hesitancy has numerous consequences that negatively affect coworkers, patients, and the healthcare system [Reference Wilpstra, Morrell, Mirza and Ralph17].CTs held by these people may foster (more) distrust towards health authorities and their recommendations, which could impede efforts to end pandemics [Reference Bertin, Nera and Delouvée18].
Methods
Search strategy
A comprehensive and systematic literature search of Medline, EMBASE, Web of Science Core Collection, Scopus, and CINAHL electronic databases (from inception to October 2023) was conducted for English, Dutch, and German studies, examining the prevalence of COVID-19-related CTs among HCWs and healthcare students, and/or factors driving HCWs into believing these theories. Full search strategies are available as Supplementary Material. Duplicates were removed by J.D., using EndNote X9. After removing duplicates, titles and abstracts were screened by H.L., using Rayyan QCRI. H.L. and J.D. did the full-text screening. Articles that were deemed potentially relevant according to the selection criteria were included. Any disagreements were solved by consensus or by the decision of a third reviewer (M.D.H.). References of the identified studies and pertinent reviews were carefully cross-checked for additional relevant studies.
Eligibility criteria
Studies were eligible for inclusion if they:
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(1) were peer-reviewed;
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(2) reported prevalence rates of COVID-19-related CTs and/or explored the determinants of these CTs;
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(3) labelled CTs as beliefs featuring a secret plot by a group of powerful elites that involve the harm of a group of people [11, Reference Robertson, Pretus, Rathje, Harris and Van Bavel13];
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(4) were conducted at a time when vaccines were available in the studied country or region;
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(5) included a population of HCWs and/or healthcare students. For defining HCWs, we used the International Standard Classification of Occupations (ISCO), also used by the WHO [19]. This classification includes health professionals (e.g., generalist medical doctors, nursing professionals, midwifery professionals, dentists, pharmacists, physiotherapists, dieticians, and nutritionists), health associate professionals (e.g., technicians for medical imaging, laboratory work, and dental prosthetics, pharmaceutical and dental assistants, community health workers, ambulance workers), personal care workers in health services (e.g., healthcare assistants, home-based personal care workers), health management and support personnel (e.g., health service managers, biomedical engineers, medical secretaries) and other health service providers.
Studies that were not peer-reviewed or published (preprints, dissertations, conference papers, books/book sections, commentary/opinion pieces), studies exclusively presenting qualitative data, case reports, and non-original research were excluded. Studies including other professions not covered by the WHO definition of HCWs (e.g., studies with first responders that also include enforcement officers and firefighters, next to HCWs, without providing separate data for HCWs), as well as studies written in other languages than English, Dutch or German were excluded. When conspiracy beliefs were not embedded into a belief system involving a secret plot, the study was also excluded.
Data extraction
Data were extracted and mapped descriptively by H.L., using a data extraction form. This form included the following information: author(s), year of publication, country/region where the study has been conducted, study design, specific population of HCWs and/or healthcare students, sample size, mean age, gender, ethnicity, vaccine hesitancy rate(s) due to CTs, and/or information on the determinants or nature of CTs. We refrained from employing meta-analytical methods due to the significant heterogeneity of the included studies regarding methodology, measures, and outcomes.
Results
Search strategy
The original search in the Medline, EMBASE, Web of Science, Scopus, and CINAHL databases yielded a total of 12,538 reports (Medline: 2,671; Embase: 3,983; Web of Science: 2,749; Scopus: 2,633; CINAHL: 502). Of these, 7,539 duplicate reports were removed (see Figure 1). Overall, 272 references of published reports were selected as potentially eligible, of which 37 reports met the inclusion criteria. Two published reports, identified through cross-reference, were added (see Figure 1) [Reference Kaya12, Reference Azimi, Yadgari and Atiq20–Reference Iliyasu, Garba, Gajida, Amole, Umar and Abdullahi57].
Figure 1. PRISMA flow chart.
Study and patient characteristics
The 39 eligible reports included 37 studies with a total of 55,556 participants. Roberts [Reference Roberts, Dubov, Distelberg, Peteet, Abdul-Mutakabbir and Montgomery42] and Dubov [Reference Dubov, Distelberg, Abdul-Mutakabbir, Peteet, Roberts and Montgomery43] extracted their data from Dubov [Reference Dubov, Distelberg, Abdul-Mutakabbir, Beeson, Loo and Montgomery44] for secondary analysis. These reports therefore were counted as one study. All studies were performed between 2021 and 2023. Most studies were conducted in the Arab world (n = 10). The other studies were conducted in Africa (not belonging to the Arab world) (n = 9), Asian countries (n = 3), or European countries (n = 6), Turkey (n = 4), and North America (n = 3). Two studies were conducted worldwide (n = 2). Of the 37 eligible studies, 33 had a cross-sectional design, 1 was a prospective cohort study, and 3 were mixed-method studies. Mean age was 32.8 years (SD = 6, range: 18–78); 58.0% of the participants were female. All patient and study characteristics of the included studies are presented in Table 1.
Table 1. Characteristics of quantitative studies, including conspiracy findings and/or correlation between different determinants and CTs among HCWs and healthcare students
CBS, Conspiracy Belief Scale; CHEO, community health extension officers; CT, conspiracy theory; DC, timing of data collection; HCW, Healthcare Worker; (a)OR, (adjusted) Odds Ratio with coincidence interval of 95%; NR, not reported; NS, not significant; *p < 0.05, **p < 0.001, ***p < 0.0001; VCBS: Vaccine Conspiracy Belief Scale.
a : Dubov (2022) and Roberts (2022) extracted their data from Dubov (2021) for secondary analysis. Bold: prevalence of CTs regarding HCWs who are vaccine hesitant; Italic: prevalence of CTs regardless of vaccination status; bold and italic: combination of HCW CT believers who are vaccine hesitant and believe in CTs regardless of vaccination status.
Prevalence and nature of COVID-19-related CTs among HCWs
Prevalence rates of COVID-19-related CTs among HCWs varied widely, ranging from 0.89 % [Reference Azimi, Yadgari and Atiq20] to 75.6 % [Reference Bereda24] (average rate across 22 studies = 21.7%, median = 14.4). Although most of the included studies reported prevalence rates regardless of the vaccination status of HCWs, approximately one-third of these reported rates for vaccine-hesitant HCWs or rates separately for vaccinated and hesitant HCWs (see Table 1). The reported prevalence rates of COVID-19-related CTs mainly concern vaccine-hesitant HCWs (although certain studies have shown that a minority of vaccinated HCWs or HCWs who accepted getting vaccinated also endorse CTs) [Reference Satti, Elhadi, Ahmed, Ibrahim, Alghamdi and Alotaibi27, Reference Konje, Basinda, Kapesa, Mugassa, Nyawale and Mirambo32, Reference Castañeda-Vasquez, Ruiz-Padilla and Botello-Hernandez55].
When comparing prevalence rates by geographical location, in general, higher rates of COVID-19-related CTs among HCWs were found in most countries of the Arab world. Studies conducted in Jordan, for example, consistently found 30% to 45.5% of their HCWs believed in CTs [Reference Rezq and AI_Zaghmouri26, Reference AlKhawaldeh, Al Barmawi, AL-Sagarat and Al Hadid30, Reference Al-Qudah, Al-Shaikh, Hamouri, Haddad, Aburashed and Zureikat37]. Studies performed in Sudan, Saudi Arabia, Kuwait, and Libya also found almost one-third to half of their HCWs believe in CTs [Reference Satti, Elhadi, Ahmed, Ibrahim, Alghamdi and Alotaibi27, Reference Habib, Alamri, Alkhedr, Alkhorijah, Jabaan and Alanzi38, Reference Elhadi, Alsoufi, Alhadi, Hmeida, Alshareea and Dokali52, Reference Al-Sanafi and Sallam54]. However, lower CT prevalence rates (2.6%-12.5%) were found in four other studies from the Arab World [Reference Almojaibel, Ansari, Alzahrani, Alessy, Farooqi and Alqurashi25, Reference Nasr, Saleh, Hleyhel, El-Outa and Noujeim45, Reference Qunaibi, Basheti, Soudy and Sultan50, Reference Shehata, Elshora and Abu-Elenin53]. Among African countries not belonging to the Arab world, the highest prevalence rates of CTs among HCWs were found in two studies from Ethiopia (30.1% and 75.6%) [Reference Bereda24, Reference Asres and Umeta36] and one from Nigeria (52.8%) [Reference Iliyasu, Garba, Gajida, Amole, Umar and Abdullahi57]. In the remaining African countries, less than 10 % of HCWs were found to believe in COVID-19-related CTs [Reference Joseph, Jerome, Boima, Pognon, Fejfar and Dibba21, Reference Konje, Basinda, Kapesa, Mugassa, Nyawale and Mirambo32, Reference Szmyd, Karuga, Bartoszek, Staniecka, Siwecka and Bartoszek47]. US studies showed heterogeneous results. While Dubov et al. found conspiracy prevalence rates up to 38 % among HCWs [Reference Dubov, Distelberg, Abdul-Mutakabbir, Beeson, Loo and Montgomery44], no conspiracy thinking was found in the study by Hoffman et al. [Reference Hoffman, Boness, Chu, Wolynn, Sallowicz and Mintas34]. Prevalence rates of COVID-19-related CTs among European HCWs were less than 10% [Reference Odejinmi, Mallick, Neophytou, Mondeh, Hall and Scrivener35, Reference Petersen, Mülder, Kegel, Röthke, Wiegand and Lieb40, Reference Szmyd, Bartoszek, Karuga, Staniecka, Błaszczyk and Radek46, Reference Szmyd, Karuga, Bartoszek, Staniecka, Siwecka and Bartoszek47, Reference Woolf, McManus, Martin, Nellums, Guyatt and Melbourne49], except for one study conducted in Croatia and Bosnia where prevalence rates of CTs among medical students reached up to 46.4% [Reference Vranić, Peloza, Jerković-Mujkić, Kustura, Ademović and Šegalo29].
While some of the included studies examined various specific COVID-19-related CTs, others did not differ between specific CTs. Although it therefore remains difficult to determine which types of CTs are more prevalent among HCWs in certain regions, compared to those in other regions, some patterns could be observed. While in European countries and Northern America, an increased belief of HCWs in the “destabilization and power gain” narrative was found [Reference Vranić, Peloza, Jerković-Mujkić, Kustura, Ademović and Šegalo29, Reference Odejinmi, Mallick, Neophytou, Mondeh, Hall and Scrivener35, Reference Roberts, Dubov, Distelberg, Peteet, Abdul-Mutakabbir and Montgomery42–Reference Dubov, Distelberg, Abdul-Mutakabbir, Peteet, Roberts and Montgomery43, Reference Szmyd, Bartoszek, Karuga, Staniecka, Błaszczyk and Radek46, Reference Szmyd, Karuga, Bartoszek, Staniecka, Siwecka and Bartoszek47], African HCWs particularly endorsed the “population reduction” and “liberty restriction” narratives [Reference Joseph, Jerome, Boima, Pognon, Fejfar and Dibba21, Reference Oyeyemi, Fagbemi, Busari and Wynn22, Reference Ben, Efanga, Ukpong and Obiora41, Reference Ditekemena, Nkamba, Mutwadi, Mavoko, Fodjo and Luhata48, Reference Iliyasu, Garba, Gajida, Amole, Umar and Abdullahi57] (see Table 2). The specific prevalence of various types of CTs along with detailed descriptions are found in Table 1.
Table 2. Types of COVID-19-related CTs (based on Fotakis & Simou, 2023) [Reference Fotakis and Simou69]
Determinants associated with CTs among HCWs
The majority of studies among HCWs did not investigate sociodemographic, psychological, religious, or political determinants of CTs. Moreover, heterogeneous results were found.
Sociodemographic determinants
Only three studies investigated the relationship between gender and CTs [Reference Joseph, Jerome, Boima, Pognon, Fejfar and Dibba21, Reference Jamil, Muhib, Abbal, Ahmed, Khan and khan39, Reference Petersen, Mülder, Kegel, Röthke, Wiegand and Lieb40]. Of these, Petersen et al. found that women tended more towards CTs than men (p<0.001) [Reference Petersen, Mülder, Kegel, Röthke, Wiegand and Lieb40]. Although Oyeyemi et al. found men to be statistically more likely to believe in “DNA alteration theory” than women, results between genders were not significant for the “microchip injection theory” [Reference Joseph, Jerome, Boima, Pognon, Fejfar and Dibba21]. Jamil et al. found no correlation between these variables [Reference Jamil, Muhib, Abbal, Ahmed, Khan and khan39].
Two studies investigating the relationship between age and CTs did not find an age-related effect [Reference Kaya12, Reference Petersen, Mülder, Kegel, Röthke, Wiegand and Lieb40].
Regarding race and ethnicity, the study of Odejinmi et al. found no significant association between ethnicity and conspiracy thinking [Reference Odejinmi, Mallick, Neophytou, Mondeh, Hall and Scrivener35]. Woolf et al. however, found Black and Asian HCWs having higher scores on the COVID-19 conspiracy beliefs scale than White people (p < 0.001) [Reference Woolf, McManus, Martin, Nellums, Guyatt and Melbourne49]. Moreover, in the US study of Dubov et al., CTs were more widespread among Hispanic HCWs than among Asian-American and African-American HCWs. These groups, however, were not compared with White HCWs [Reference Dubov, Distelberg, Abdul-Mutakabbir, Peteet, Roberts and Montgomery43].
Several studies found an association between educational level or profession and conspiracy endorsement. Kaya et al. demonstrated that HCWs with higher educational levels (master’s and doctorate degrees) believed significantly less in CTs, in comparison to HCWs with a bachelor degree and lower educational level [Reference Kaya12]. In general, it seems that particularly nurses and non-clinical and administrative staff stand out as having significantly higher levels of CT beliefs. For example, in a German study, CTs were found to be significantly more prevalent among nursing, medical technical, and administrative staff, in comparison to physicians and scientific staff [Reference Petersen, Mülder, Kegel, Röthke, Wiegand and Lieb40]. In a study from Nigeria, nurses were significantly more likely to believe in CTs than physicians [Reference Oyeyemi, Fagbemi, Busari and Wynn22].
Political orientation, government trust, information sources, and religious beliefs
A U.S. study found that the group of HCWs who had the highest rate of CTs were lean Republicans while the group with the lowest CTs rates were Democrats [Reference Dubov, Distelberg, Abdul-Mutakabbir, Beeson, Loo and Montgomery44]. One study conducted in Nigeria showed that the odds of believing in the microchip theory increased significantly with a decreasing level of trust in the government’s information regarding the COVID-19 pandemic and vaccines (odds ratio [OR] 4.6, 95% CI 2.6–8.0), when compared to those with a high level of trust. Findings were similar for those who believed in the DNA alteration theory (OR 5.2, 95% CI 3.1–8.8) [Reference Oyeyemi, Fagbemi, Busari and Wynn22].
Regarding information sources, HCWs who were more dependent on social media, TV programs, and popular newspapers had a higher score on the Vaccine Conspiracy Belief Scale, compared to those who relied on information provided by scientists, doctors (or HCWs in general), or scientific journals [Reference Al-Sanafi and Sallam54]. In line with these findings, Oyeyemi et al. found HCWs using health authorities as the main source of information to be less likely to believe in CTs about microchips (OR 0.4, 95% CI 0.2–0.7) and the “DNA alteration theory” (OR 0.5, 95% CI 0.3–0.9) [Reference Oyeyemi, Fagbemi, Busari and Wynn22].
No study was found examining the relationship between religion and CTs among HCWs.
Psychological aspects
One large international study (n = 12,792) suggested that HCWs with current depressive symptoms had a higher overall tendency to believe in CTs [Reference Fountoulakis, Karakatsoulis, Abraham, Adorjan, Ahmed and Alarcón28].
Discussion
Our scoping review has shown that HCWs are not immune to CTs. Although prevalence rates of COVID-19-related CTs varied considerably (ranging from 0.89% to 75.6%), they generally appeared to be higher among HCWs in most countries of the Arab world, Ethiopia, and Nigeria, in comparison to those in other African and most Western countries. Limited and heterogeneous data prevented conclusive findings on determinants associated with CTs among HCWs. The only consistent observation was that HCWs with higher educational attainment tend to endorse CTs less frequently.
The wide variance in prevalence rates of COVID-19-related CTs among HCWs is in line with the results that have been found in the general population (prevalence rates ranging from 0.4% to 82.7%) [Reference Tsamakis, Tsiptsios, Stubbs, Ma, Romano and Mueller58, Reference Fountoulakis, Karakatsoulis, Abraham, Adorjan, Ahmed and Alarcón59]. Despite this wide range, our results suggest that geographical variations exist, with higher prevalence rates in most countries of the Arab world and some countries on the African continent. One potential explanation for this phenomenon is the instability in most of these regions, stemming from political, economic, and/or religious conflicts, as well as natural disasters [Reference Oyeyemi, Fagbemi, Busari and Wynn22, Reference Jamil, Muhib, Abbal, Ahmed, Khan and khan39, Reference Shakeel, Mujeeb, Mirza, Chaudhry and Khan60–Reference Sallam, Dababseh, Eid, Al-Mahzoum, Al-Haidar and Taim62]. To date, studies have identified two nation-level variables that consistently predict CTs across multiple datasets: lack of economic vitality and the presence of corrupted undemocratic regimes. Thus people will believe CTs more when their perceptions of current and future economic performance within their nation are relatively poor, and when electoral processes are distorted, civil liberties restricted, and official media are mouthpieces for government propaganda [Reference Hornsey, Bierwiaczonek, Sassenberg and Douglas63] This results in ineffective governance and initiatives, fostering mistrust and leading to a conspiracy mentality. Another potential explanation is that nations that are high in collectivism are also more likely to endorse CTs. Collectivist cultures (and collectivism-oriented individuals) are more likely to make relational explanations when attributing causality to ambiguous events, which in turn could lead to CT endorsement [Reference Hornsey, Bierwiaczonek, Sassenberg and Douglas63]. Finally, historical (or even present) marginalization of certain groups of people or historical examples of abuse (e.g., unethical practices by pharmaceutical companies) may make CTs attractive in these countries [Reference Oyeyemi, Fagbemi, Busari and Wynn22, Reference Enders, Uscinski, Klofstad and Stoler64–Reference Yıldırım, Serçekuş and Özkan66]. In European countries, the prevalence of COVID-19-related CTs among HCWs remained under 10% [Reference Odejinmi, Mallick, Neophytou, Mondeh, Hall and Scrivener35, Reference Petersen, Mülder, Kegel, Röthke, Wiegand and Lieb40, Reference Szmyd, Bartoszek, Karuga, Staniecka, Błaszczyk and Radek46, Reference Szmyd, Karuga, Bartoszek, Staniecka, Siwecka and Bartoszek47, Reference Woolf, McManus, Martin, Nellums, Guyatt and Melbourne49], which is in line with the results that have been reported by the ECDC (European Centre for Disease Prevention and Control) [67]. Western countries usually are economically and politically more stable. However, the recent shift towards more radical right-wing political authoritarian orientations could become a fueling factor for endorsing more CTs [Reference Hornsey, Bierwiaczonek, Sassenberg and Douglas63, Reference Imhoff, Zimmer, Klein, António, Babinska and Bangerter68]. Certain patterns in the prevalence of specific types of CTs among HCWs were observed in particular regions, aligning with the findings of Fotakis’s study on the general population. For example, medical students in Bosnia and Croatia exhibited a strong belief in “Big Pharma plots” [Reference Vranić, Peloza, Jerković-Mujkić, Kustura, Ademović and Šegalo29], a trend also noted in the general population across the Balkan region [Reference Fotakis and Simou69].
As mentioned above, limited and heterogeneous data prevented conclusive findings on determinants associated with CTs among HCWs. Studies investigating age and gender-related associations with conspiracy thinking in HCWs generally found no significant relationship. A recent large-scale study, including data from 21 different countries, only found age to be (negatively) correlated with conspiracy thinking [Reference Enders, Uscinski, Klofstad and Stoler64]. Although our data on race and ethnicity are difficult to interpret, in general, it is known that CTs flourish particularly among cohesive minority groups that are suppressed by a dominant majority coalition [Reference Tsamakis, Tsiptsios, Stubbs, Ma, Romano and Mueller58, Reference van Prooijen and van Vugt70]. The above-mentioned large-scale, multicultural study found Black identification to be positively related to conspiracy thinking [Reference Enders, Uscinski, Klofstad and Stoler64]. Regarding the level of education, three studies were found showing that HCWs with higher educational levels (master’s and doctorate degrees) believed significantly less in CTs, in comparison to HCWs with bachelor’s degrees and lower educational levels (nurses, medical-technical and administrative staff) [Reference Kaya12, Reference Oyeyemi, Fagbemi, Busari and Wynn22, Reference Petersen, Mülder, Kegel, Röthke, Wiegand and Lieb40]. These results are in line with the results of studies on vaccine hesitancy that have been conducted in HCWs [Reference McCready, Nichol, Steen, Unsworth, Comparcini and Tomietto7]. Particularly the finding regarding nurses raises concerns as these are involved in many different aspects of immunization and often provide direct care to patients with COVID-19.
Only one study included in our review examined the relationship between psychological factors and CTs among HCWs, finding that HCWs with current depressive symptoms have higher CT rates [Reference Fountoulakis, Karakatsoulis, Abraham, Adorjan, Ahmed and Alarcón28]. Studies among the general population, however, have also shown that personality traits such as low tolerance for uncertainty and ambiguity, impulsivity, low perceived risk, lower analytical thinking, and negative emotions are significantly associated with belief in CTs [Reference Tsamakis, Tsiptsios, Stubbs, Ma, Romano and Mueller58, Reference van Mulukom, Pummerer, Alper, Bai, Čavojová and Farias71, Reference Staszak, Maciejowska, Urjasz, Misiuro and Cudo72]. Several studies have found that people who score higher on CT belief scales also score higher on self-report measures of schizotypal personality traits and paranoid ideation. An important side note is that CTs are not reducible to paranoia; the main difference is that CTs focus mostly on elite groups and are convinced they attack a specific population, whereas paranoid people tend to see themselves as a target [Reference Hornsey, Bierwiaczonek, Sassenberg and Douglas63].
Our study shows that most HCWs who believe in CTs, are also vaccine hesitant. As in general, studies consistently report a significant negative association between belief in COVID-19-related CTs and vaccination intention or uptake [Reference Taubert, Meyer-Hoeven, Schmid, Gerdes and Betsch73].
Vaccination hesitancy among HCWs not only poses a threat to global health efforts fighting the COVID-19 pandemic, it may also fuel public fear and erode trust in the healthcare system [Reference Roberts, Dubov, Distelberg, Peteet, Abdul-Mutakabbir and Montgomery42, Reference Grace74]. Therefore, the following recommendations can be implemented to reduce the likelihood of CTs among HCWs.
Delivering counterarguments to people before they encounter CTs (i.c. prebunking), has been shown to increase vaccine willingness, compared to people already exposed to CTs [Reference Douglas, Sutton and Cichocka75, Reference Dow, Wang, Whitson and Deng76, Reference Jolley and Douglas77]. Moreover, exposing the manipulative persuasion tactics used to spread CTs (such as the use of emotional language, misleading rhetoric, or fake experts that sow doubt about the scientific consensus) may also reduce the likelihood of adapting CTs [Reference Douglas, Sutton and Cichocka75, Reference Jolley and Douglas77]. Another effective preventive approach is to encourage people to be more critical consumers of CTs before they are first exposed to these by stimulating metacognitive reflection or critical thinking [Reference Douglas, Sutton and Cichocka75, Reference Jolley and Douglas77, Reference Salovich and Rapp78].
Once they are established, health-related CTs may be extremely resistant to correction [Reference Marques, Douglas and Jolley79]. Confrontation by simply presenting fact-based anti-conspiracy arguments may even strengthen CTs [Reference Detraux80, Reference Lazić and Žeželj81]. Although an open-minded approach through the use of empathy and active listening by inviting the person towards a deeper examination of the building bricks of their CTs is more productive [Reference Marques, Douglas and Jolley79, Reference Detraux80], it only showed small effects [Reference Anderer82, Reference Holford, Schmid, Fasce and Lewandowsky83]. Thus, simply giving people the “right” set of facts does not guarantee that they will adopt desirable beliefs or engage in advisable behaviors. One must also recognize the role of people’s motivations in believing these theories [Reference Enders, Uscinski, Klofstad and Stoler64]. Many people with CTs incorrectly believe that their hesitancy to be vaccinated is rather common and overestimate how much others believe anti-vaccine CTs. One therefore should highlight that CTs are not as commonplace as they may think, for example by using normative feedbackFootnote 1, preferably in the context of a relevant social group [Reference Dow, Wang, Whitson and Deng76, Reference Marques, Douglas and Jolley79, Reference Cookson, Jolley, Dempsey and Povey84]. Healthcare leaders could act as role models by being a trusted source of information and creating new social norms by getting publicly vaccinated and explicitly expressing the benefits of vaccination. This way, they can convey through their actions that getting vaccinated is safe and beneficial and connect it to a shared collective identity and enhance feelings of control and self-efficacy of their employees [Reference Dow, Wang, Whitson and Deng76].
Several authors endorse the use of vaccine mandates to lessen the deleterious effects of CTs [Reference Dow, Wang, Whitson and Deng76, Reference Lewandowsky, Holford and Schmid85]. Although mandatory vaccination interferes with the right to private life, the exceptions under Article 8 of the European Convention on Human Rights (in particular the protection of public health and the protection of the rights and freedom of others) might justify these interferences [Reference Simons, Ploem and Legemaate86]. Moreover, fear of social sanctions can be a powerful motivator. Although this approach has been shown effective [Reference Lytras, Di Gregorio, Apostolopoulos, Naziris, Zingerle and Heraclides87], it does not target vaccine hesitancy and may actually arouse suspicions, thereby encouraging CTs [Reference Enders, Uscinski, Klofstad and Stoler64].
Regardless of the above-mentioned recommendations, it is important to know that HCWs holding CTs probably are not a homogeneous group. Research has shown that next to COVID-19 conspiracy “believers” and “non-believers”, there also exist COVID-19 conspiracy “ambivalent believers” (i.c. vaccine hesitant COVID-19 CT believers who are less likely to believe CTs than COVID-19 conspiracy “believers” as they are less misinformed or uninformed about the COVID-19 vaccine. This explains why this group is more uncertain, ambivalent, and undecided about the COVID-19 vaccine than the “believers”). All these groups differ in terms of psychological characteristics [Reference Roberts, Dubov, Distelberg, Peteet, Abdul-Mutakabbir and Montgomery42, Reference Dubov, Distelberg, Abdul-Mutakabbir, Beeson, Loo and Montgomery44, Reference Celia, Lausi, Girelli, Cavicchiolo, Limone and Giannini88]. The need to tailor interventions for HCWs believing in COVID-19 CTs therefore is necessary.
Strengths and limitations
A key strength of this analysis is the extensive search strategies including several databases (see Supplementary Material). One major limitation of this study is the exclusion of qualitative data, which give the opportunity to understand more deeply why HCWs believe in CTs. Moreover, heterogeneity across studies in terms of tools, methods, and survey designs made it hard to perform a thorough quantitative analysis of the data. Although we didn’t critically appraise the included studies, we also noticed that several of these studies were poorly performed. Furthermore, we surmise that the actual number of HCWs with conspiracy beliefs may be higher than our results indicate. There may be unidentified “unspoken vaccine hesitancy” cases, a phenomenon where HCWs do not express publicly their hesitancy and potentially conspiratorial concerns about vaccines due to institutional and societal pressure and out of fear of being mocked or stigmatized [Reference Tucak and Vinković89]. Finally, the majority of the included studies had a cross-sectional design, which does not allow us to infer causal relationships.
Conclusion
Although COVID-19-related CTs may be highly prevalent among HCWs, gaps in understanding the drivers of CTs among HCWs remain. Given HCWs’ critical role in public health, especially during pandemics, further research is therefore essential to mitigate the impact of CTs on vaccine willingness among HCWs.
Supplementary material
The supplementary material for this article can be found at http://doi.org/10.1192/j.eurpsy.2025.12.
Data availability statement
The analysis is based on the content of the selected publications.
Author contribution
H.L, J.D., and M.D.H. conceptualized the study. J.D. outlined the search strategy. H.L. and J.D. performed the literature search. H.L. wrote the draft of the manuscript. J.D. and M.D.H. gave feedback on drafts of the manuscript. H.L. and J.D. revised the manuscript. All authors have read and approved the manuscript.
Financial support
This research received no external funding.
Competing interests
The authors declare no competing interests.
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